Fuel pressure issues

[Jrnelson]

I have an ‘08 suburban 2500 6.0 L. I had driven the vehicle and parked at my house. Then a couple hours later went to leave and the vehicle would crank but not start. I discovered no fuel pressure so I replaced the fuel pump in the tank above the spare tire. The vehicle started up and drove fine for a couple of weeks then died again. I still had good pressure at the fuel rail so I changed all 8 injectors. Now the vehicle will crank but not start again. I have no fuel pressure at the fuel rail. I have a good fuse and relay. I found what looks to be a larger fuel tank in front of the rear axle that I was unaware of.

my questions are: 1st-what an I missing and why won’t my rig start. 2nd-could there be a second fuel pump in the larger tank that has now inconveniently failed. 3rd-how do the 2 tank work/is the smaller tank like a reserve tank. 4th-HELP!?

 

[zora]

Both tanks have pumps.
When the level in the primary tank hits a certain low level it triggers a relay turning on the secondary pump which fills the primary tank.

 

[Jrnelson]

Both tanks have pumps.
When the level in the primary tank hits a certain low level it triggers a relay turning on the secondary pump which fills the primary tank.

Thanks for the feedback. I have done some more troubleshooting and I’m still not getting fuel back to the fuel rail after replacing the injectors. I replaced 2 different relays to make sure they were good. I have a good fuse, but no power at the fuel pump fuse with the ignition on. Is there a 3rd relay or a fuel control module somewhere that might be keeping the system from powering the fuel pump?

 

[zora]

If you google 2008 suburban fuel wiring diagram you will find a circuit diagram